Back rest



FIG. 1 is a perspective view of a back rest, showing my new design;

FIG. 2 is a back side view thereof;

FIG. 3 is a front side view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top side view thereof; and,

FIG. 7 is a bottom side view.

CLAIM The ornamental design for a back rest, as shown and described.